1. Field of the Invention
The field of the invention is that of analog signal processing. Analog signal processing includes amplifying a signal before analog to digital conversion, for example, and can be carried out only on a signal having sufficient energy, since the processing usually consumes a great deal of energy. A signal to be processed is usually a low-energy signal and it is therefore necessary to amplify the signal to increase its energy before it is processed.
The invention concerns an amplifier device for increasing the energy of a signal so that it can be processed.
The invention can be implemented in a differential electronic circuit, for example. In this case amplifier devices of the invention can alternate with filter stages.
More generally, the invention is applicable whenever a device has to provide a gain (often relatively low).
2. Description of the Prior Art
There are various types of prior art amplifier device.
Some prior art amplifier devices use a non-differential structure. This non-differential structure has various drawbacks, including high levels of noise and offset.
Other prior art amplifier devices use a differential structure. This differential structure does not give rise to any significant noise or offset, but nevertheless has drawbacks.
In a voltage mode differential structure the value of the gain is difficult to control, the energy consumption can only be low, to the detriment of speed, and achieving a high bandwidth necessitates high current consumption.
A current mode differential structure palliates the drawbacks associated with a non-differential structure but there is unwanted common mode gain.
Finally, amplifier devices based on this differential structure, whether they are voltage mode or current mode devices, are usually operational amplifiers, i.e. devices intended always to be used with feedback.
Operational amplifiers are used with feedback, even if a low gain is required. For example, it is routine practice to use an operational amplifier having a high gain (equal to 1,000, for example) in open loop mode to obtain a low gain (equal to 10, for example) in closed loop mode. This obviously entails excess current consumption.